The purpose of this project is to develop systems for measuring oxygen concentrations on and inside the eye. These systems will take advantage of phosphorescent probes that are sensitive to oxygen concentrations. They will have obvious applications in eye research and will lead to advancements in our understanding of ocular diseases, development of new drugs, contact lenses and surgical procedures. It should be emphasized that these instrument systems are aimed solely at the ophthalmic research market, and NOT at the clinical diagnostic market. We believe that there is both a significant demand for such products in this market, and that their use will have significant impact to our understanding of oxygen in the eye, its role in ocular disease, and the development of new drugs, contact lenses, other therapeutic devices, and surgical procedures. Our initial technique used a dual frequency photon counting system, which we developed specifically for this purpose. It combined maximum sensitivity with the ability to measure a wide range of oxygen concentrations. During Phase I, we demonstrated feasibility of our techniques both in vitro and in the rabbit eye. These studies indicated that we could use a more flexible programmable photon counting system that could span a wide range of frequencies allowing the use of a wide range of phosphorescent probes. Since the last revision of this application, we have implemented this new design and tested it with both in vitro solutions and with live rabbits. There are a wide range of phosphorescent dyes available, and we propose to characterize many of them for their ability to penetrate or not penetrate into different ocular tissue. Phosphorescence quenching is not limited to oxygen. The dye system used in Phase I has previously been shown to be relatively insensitive to other ocular variables, but any new dyes will also have to be characterized similarly. A number of animal systems including humans have been used in previous research on ocular oxygen. We intend to leverage three delivery platforms developed by OcuMetrics to access the full range of animal systems: humans, laboratory animals (primates, rabbits, etc.), and very small laboratory animals (mice). Our overall goal is to develop multiple measurement systems based on dyes that have been selected for specific environmental affinity, oxygen range, etc. A critical goal will be standardization and calibration control, so that results made on different machines will be comparable. In addition, we will design this instrument with enough flexibility so that we can add capabilities as new phosphorescent oxygen probes and techniques are developed. PUBLIC HEALTH RELEVANCE: Oxygen is fundamental to life, but its presence is not only life giving, its reactive nature can also lead to dysfunction. The proposed instrument will take advantage of phosphorescent probes that are sensitive to oxygen concentrations to monitor oxygen concentrations in various areas of the eye. This will have obvious applications in eye research, and drug and contact lens testing.